Photorefractive Keratectomy for Mild-to-Moderate Myopics with Thin Corneas: A 3-Year Follow-up Results

Abstract

Background: The purpose of this study was to evaluate the 3-year visual outcomes in mild-to-moderate myopic patients with thin corneas who underwent photorefractive keratectomy (PRK) with or without mitomycin C (MMC).
Methods: Thirty myopic eyes with a mean spherical equivalent (SE) of −3.76 ± 1.72 (−6.50 to −1.25) diopter (D) and a mean corneal thickness of 486.03 ± 11.93 (452-499) µm at the thinnest point underwent PRK. MMC was used if they had > 4.0 D myopia. All surgeries were performed with the VISX STAR S4 Excimer Laser (Abbott Medical Optics, Abbott Park, Illinois, USA).
Results: Uncorrected visual acuity showed a significant improvement 3 years after surgery when compared to baseline and reached 0.01 ± 0.04 LogMAR (P < 0.001). Best-corrected visual acuity was 0.00 ± 0.01 LogMAR preoperatively and did not change significantly postoperatively. Spherical (P < 0.001) and cylindrical (P < 0.001) error significantly decreased. Manifest refraction SE showed a significant decrease when compared to before the operation and reached −0.08 ± 0.16 D (P < 0.001). At 3 years, mesopic contrast sensitivity was not significantly different from baseline at any spatial frequency. Vertical coma showed a significant decrease and reached −0.10 ± 0.27 µm (P = 0.004). Total coma (P < 0.001), spherical aberration (P < 0.001), and total high order aberrations (P < 0.001) also increased significantly.
Conclusions: Based on the 3-year results, PRK (+MMC in patients with SE > 4.0 D) is a safe, effective, and predictable treatment option for mild-to-moderate myopic patients whose minimum corneal thickness is < 500 µm.